Liquid Crystal Display (LCD) possesses advantages of high image quality, power saving, thin body and wide application scope. Thus, it has been widely applied in various consumer electrical products, such as mobile phone, television, personal digital assistant, digital camera, notebook, laptop, and becomes the major display device.
In the active matrix liquid crystal display, each pixel has a thin film transistor (TFT). The gate thereof is connected to the horizontal scanning line, the source thereof is connected to the data line in the vertical direction, and the drain thereof is connected to the pixel electrode. Applying enough voltage on the horizontal scanning line will turn on all TFTs on this line. At this time, the pixel electrodes on the horizontal scanning line will be connected with the data lines in the vertical direction, then write the display signal on the data lines into pixel, and control various liquid crystal transmittances to control the color.
Generally, the liquid crystal display panel comprises a CF (Color Filter) substrate, a TFT (Thin Film Transistor) substrate, LC (Liquid Crystal) sandwiched between the CF substrate and TFT substrate and sealant. The formation process generally comprises: a forepart Array process (thin film, photo, etching and stripping), a middle Cell process (Lamination of the TFT substrate and the CF substrate) and a post module assembly process (Attachment of the driving IC and the printed circuit board). The forepart Array process is mainly to form the TFT substrate for controlling the movement of the liquid crystal molecules; the middle Cell process is mainly to add liquid crystal between the TFT substrate and the CF substrate; the post module assembly process is mainly the driving IC attachment and the integration of the printed circuit board. Thus, the liquid crystal molecules are driven to rotate and display pictures.
With the curving panel market be increased, the widely use the COA (Color filter On Array) and POA (Photo Spacer On Array) process, and preparing the RGB filter and the photo spacer on the array substrate could effective avoid color shift at large viewing angle and risk of the light leakage.
However, if using the COA and POA process, PI (polyimide) aligning film of the CF substrate cannot control accuracy coating while made the PI aligning film by the inject process. In order to avoid the unevenness of the image display caused by the unevenness PI films, the PI aligning film of the CF substrate will be coated over the sealant usually, and entirely covering CF substrate. It cause the water vapor easily enter to inside the panel by PI aligning film on the CF substrate, and cause life time of inside elements of the panel be shortened or inner circuit of the panel corrosion, cause abnormal panel display.